This invention relates to electric heating elements used to heat a tobacco flavor generating medium in an electrical smoking article. In particular, this invention relates to such a heating element arranged in a tubular array.
One type of electrical smoking article is disclosed in commonly-assigned U.S. Patent No. 5,060,671, which is hereby incorporated by reference in its entirety. In such an electrical smoking article, a flavor bed of a tobacco flavor medium, such as tobacco or tobacco-derived substances, is heated electrically to release a tobacco flavor substance without burning. As the tobacco flavor medium is heated, a smoker at the mouth or downstream end of the device draws air in and around the heating element by inhaling, and thereby receives the tobacco flavor substance.
The above-identified application discloses a number of possible heater configurations, many of which are made from a carbon composite material formed into a desired shape. For example, one configuration involved a radial array of blades connected in common at the center and separately connectable at their outer edges to a source of electrical power. By depositing tobacco flavor medium on each blade and heating the blades individually, one could provide a predetermined number of discrete puffs to the smoker. Other configurations included various linear and tubular shapes, subdivided to provide a number of discrete heating areas.
Other configurations have been proposed. For example, various arrays of discrete fingers or blades of heater material can be provided, each blade providing one puff. However, suitable heater materials, such as those described in said above-incorporated U.S. Pat. No. 5,060,671 are generally not strong enough to be arranged in such a blade configuration without threat of blade breakage. This is particularly true of a preferred material made by mixing carbon, fillers and binders and curing and heating the mixture until the desired resistivity is achieved. This material has been found to have the proper electrical resistivity characteristics and evolves no undesirable constituents when heated to operating temperature.
Further, as disclosed in said above-incorporated U.S. Pat. No. 5,060,671, such heating elements are preferably disposable and replaceable. Therefore, they must be relatively inexpensive to produce.
It would be desirable to be able to provide an array of heater blades or fingers that is sufficiently strong for use in an electrical smoking article without danger of breakage.
It is also desirable to be able to provide such an array of heater blades that is sufficiently inexpensive to manufacture that it can be disposable.